Does anyone know how much current this relay needs for its coil to turn on? And what's its coil resistance? Here is the datasheet: Finder 40.61 It's a 12v DC relay. And how can I turn it on using a microcontroller PIN?
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1\$\begingroup\$ There are 25 variants of that relay including DC and AC coil versions. Which one do you want to use? What is the relay coil supply voltage going to be? Edit your question to include that information. \$\endgroup\$– TransistorCommented Dec 29, 2021 at 8:41
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1\$\begingroup\$ (1) How much coil current depends on input voltage. Usually 5V needs 70mA, 12V needs less, for the same power (See reference below). (2) You can use a 3V3/5V0 MPU/SBC GPIO pin to turn on/off, with the help of a transistor, usually NPN BJT. You also need a flyback diode, and an optocoupler, if environment is noisy. (3) Reference: My answer to this EESE Relay Q&A: electronics.stackexchange.com/questions/505318/… \$\endgroup\$– tlfong01Commented Dec 29, 2021 at 8:57
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1\$\begingroup\$ @tlfong01 Thanks \$\endgroup\$– MomoCommented Dec 29, 2021 at 9:19
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1\$\begingroup\$ @tlfong01. How would an opto help? Optos give galvanic isolation but can still couple fast transients due to their capacitance. \$\endgroup\$– KartmanCommented Dec 29, 2021 at 11:56
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1\$\begingroup\$ @tlfong01 I'm no stranger to these effects. I don't need to tell you that a well placed diode negates these effects to a significant degree. The voltage is clamped and has a well defined path, so the opto will have little benefit. You've yet to convince me how in a circuit with a microcontroller and a relay would benefit from an opto in the relay drive in a correctly designed and laid out circuit. \$\endgroup\$– KartmanCommented Jan 1, 2022 at 5:27
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1 Answer
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Figure 1. From datasheet.
From \$ P = VI \$ we can calculate \$ I = \frac P V = \frac {0.65}{12} = 53\ \mathrm{mA} \$.
simulate this circuit – Schematic created using CircuitLab
Figure 2. An NPN switching circuit.
answered Dec 29, 2021 at 9:00
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1\$\begingroup\$ Thank you. Can you also see what's the coil resistance? \$\endgroup\$– MomoCommented Dec 29, 2021 at 9:19
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1\$\begingroup\$ Do you know the formula that relates power, voltage and resistance? \$\endgroup\$ Commented Dec 29, 2021 at 10:35
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